During operation, gas turbine engines, whether used for flight or stationary power generation, develop extremely high temperature and high velocity gases in a combustor portion of the engine. These gases are ducted on blades of a turbine rotor to cause rotation of the rotor and are redirected by the stator vanes onto additional rotor blades to produce more work. Because of the high heat of the gases, it is desirable to cool the blades and vanes to prevent damage and, to extend the useful life of, these engine components. It is known in the art that turbine components can be cooled by film cooling that is provided by a plurality of cooling holes. These holes are small have a complex shape; and often, there is a large number of cooling holes in the surface to be cooled.
After the cooling holes have been manufactured, it is necessary to inspect each of the holes to determine whether it exists and is properly formed as a complex hole. One method of inspection is a manual method in which an inspector is provided with a drawing of the desired hole pattern and a pin. The inspector first confirms that a hole exists at each location identified by the pattern; and then, the inspector inserts the pin through each of the holes to determine whether the hole is properly drilled as a through-hole. As can be appreciated, such an inspection process is highly repetitive, tedious and stressful for the inspector and, in addition, is expensive and inefficient for the manufacturer of the turbine component. Other inspection processes are known that are somewhat less tedious, but all of the processes known to applicant are based on human visual inspection.
Thus, there is a need for an inspection apparatus and process that can automatically inspect complex cooling holes in gas turbine components faster, more precisely and less expensively than known devices and methods.